Heme synthetase deficiency in human protoporphyria. Demonstration of the defect in liver and cultured skin fibroblasts.

A B S T R A C T In this paper we show that the ferrochelatase defect in erythropoietic protoporphyria (EPP) can readily be identified in mitogen-stimulated lymphocytes since such cells from patients with EPP accumulate approximately twice as much protoporphyrin IX as cells from normal subjects when incubated with a porphyrin precursor, 6-aminolevulinic acid (ALA). Treatment of cultures with ALA and with the iron chelator, CaMgEDTA significantly increased the level of protoporphyrin IX in mitogen-stimulated lymphocytes from normal subjects, while the same treatment failed to produce an increase in protoporphyrin IX in cell preparations from EPP patients. In contrast to the results with the chelator treatment, supplementation of the cultures with iron and ALA reduced the level of protoporphyrin IX in normal cells, but not in EPP cells. These findings are compatible with a partial deficiency of ferrochelatase in EPP lymphocytes. The gene defects of acute intermittent porphyria and hereditary coproporphyria have previously been identified using lymphocyte preparations from the gene carriers of these diseases. The present study demonstrates that EPP represents another form of human porphyria in which the gene defect of the disease can now be identified in lymphocyte preparations.

Section: Introductionmentioning

confidence: 99%

Studies in porphyria: functional evidence for a partial deficiency of ferrochelatase activity in mitogen-stimulated lymphocytes from patients with erythropoietic protoporphyria.

Sassa¹,

Zalar²,

Poh–Fitzpatrick³

et al. 1982

“…Protoporphyria is an inherited disorder of porphyrin metabolism in which deficiency of heme synthase leads to overproduction of protoporphyrin (1)(2)(3)(4)(5). The initial manifestation and dominant symptom of the disorder is a photodermatitis characterized by erythema, edema and pain (1,6,7).…”

Section: Introductionmentioning

confidence: 99%

Protoporphyrin-induced Cholestasis in the Isolated In Situ Perfused Rat Liver

Avner¹,

Lee²,

Berenson³

1981

A B S T R A C T The pathogenesis of liver disease in protoporphyria has been presumed to result from the hepatic deposition of protoporphyrin. To examine the effects of protoporphyrin on hepatic bile flow and histopathology, studies were performed employing an isolated, in situ, rat liver perfusion system. Rat livers in the control group were perfused with 0-80 umol sodium taurocholate/h. Rat livers in the experimental group were perfused with sodium taurocholate and (a) sufficient quantities of protoporphyrin to produce maximal canalicular secretion and (b) perfusate protoporphyrin concentrations of 0.01, 0.1, and 1 ,tM.The administration of protoporphyrin sufficient to achieve maximal canalicular secretion was found to significantly reduce bile flow in rats infused with 0, 40, and 80 ,imol sodium taurocholate/h. Linear regression analysis defined the relationship between bile flow and biliary bile acid secretion and showed that the bile acid-independent fraction ofbile flow was reduced (P < 0.01). Bile acid-dependent flow was unaffected and there was no significant difference in biliary bile acid secretion rates between control and protoporphyrin-perfused livers. Perfusion of rat livers with varying concentrations of protoporphyrin demonstrated the reduction of bile flow was dose-related. Analysis of perfusate enzyme activity did not reveal abnormalities that could account for the cholestasis. Studies to evaluate the effect of protoporphyrin on regional hepatic hemodynamics were inconclusive.Histopathological studies of control and protoporphyrin-perfused rat livers did not show ab-

“…Since this enhancement only seemed to occur in those experiments in which griseofulvininduced porphyrogenesis was continuously stimulated, it may be speculated that "newer" protoporphyrin in the hepatocyte is more readily mobilized for such accelerated secretion, while "older" deposits are less accessible. Since large amounts of protoporphyrin in livers of patients with protoporphyria are thought to be cleared from the plasma and transported into bile relatively efficiently (as reflected by the large amounts of fecal protoporphyrin excreted daily) (1,3,4,6,8,9,13,15,16,30), an important fraction of total intrahepatic protoporphyrin of these patients may be of such a relatively labile type. Other explanations may be speculated as well.…”

Section: Discussionmentioning

confidence: 99%

“…The progressive functional deterioration and death of hepatocytes associated with massive crystalline protoporphyrin deposition and cirrhosis are now well-recognized complications of this disease (1)(2)(3)(4)(5)(6)(7). Partial deficiency of the enzyme heme synthase (8) results in accumulation of protoporphyrin, a hydrophobic heme precursor. In human protoporphyria, the majority of the excess protoporphyrin is produced in the erythron; however, variable contributions to the total may derive from disordered hepatic heme synthesis in different patients (9,10).…”

Section: Introductionmentioning

confidence: 99%

Protoporphyrin hepatopathy. Effects of cholic acid ingestion in murine griseofulvin-induced protoporphyria.

Poh–Fitzpatrick¹,

Sklar²,

Goldsman³

et al. 1983

A B S T R A C T Short-term effects of cholic acid ingestion on hepatic accumulation, fecal excretion, and blood levels of protoporphyrin were studied in vivo in griseofulvin-induced protoporphyric mice. Experimental mice that received feed with 2% griseofulvin and 0.5% cholic acid were compared with control mice that received feed with 2% griseofulvin for 4 wk. Five mice from each group were assessed each week for liver and blood porphyrin levels. Fecal protoporphyrin was compared weekly in the total pooled output of each population. Mean protoporphyrin levels were significantly lower for liver (P < 0.0001), erythrocytes (P < 0.05), and plasma (P < 0.05), and higher for feces (P < 0.001) for the mice that were fed cholic acid. Microscopic protoporphyrin deposits, inflammation, necrosis, and dysplasia were more severe in livers of control mice. A second experimental design compared four regimens in the feed given to all mice after 1-wk induction with 2% griseofulvin: (a) 0.5% cholic acid, (b) no adulterant, (c) 2% griseofulvin and 0.5% cholic acid, and (d) 2% griseofulvin. No difference in protoporphyrin removal from livers of mice in groups 1 and 2 was observed after 1 and 2 wk of these regimens. The apparent reduction in hepatic protoporphyrin content in mice of group 3 as compared with group 4 at weeks 2 and 3 was not significant at P < 0.05.These data suggest that in selected circumstances, Drs. Sklar and Goldsman participated in these studies during student research elective periods at Columbia University College of Physicians and Surgeons. Address all correspondence to Dr. Poh-Fitzpatrick.